id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
34881	Model-rename migration fails with IntegrityError if m2m relations to self exist	dennisvang	nobody	"== Description

Please consider the (contrived) minimal example below, part of an app called `myapp`:

{{{
class Person(models.Model):
    name = models.CharField(max_length=255)
    children = models.ManyToManyField(
        to='self', through='myapp.Relation', blank=True
    )


class Relation(models.Model):
    parent = models.ForeignKey(
        to='myapp.Person',
        related_name='relations_as_parent',
        on_delete=models.CASCADE,
    )
    child = models.ForeignKey(
        to='myapp.Person',
        related_name='relations_as_child',
        on_delete=models.CASCADE,
    )
}}}

Now suppose I rename the `Person` model to `Foo` and update corresponding references.

Then I run `manage.py makemigrations`, which correctly recognizes that the model has been renamed.

Now, applying this migration to an empty database works, without issue, but applying the migration to a database with existing data fails with an `IntegrityError`.

== Steps to reproduce

1. start a new project, start a new app called `myapp`, with models as above.
2. run `makemigrations` and `migrate`
2. Load (valid) data from the following fixture:
{{{
[
  {""model"": ""myapp.person"", ""pk"": 1, ""fields"": {""name"": ""Jenny""}}, 
  {""model"": ""myapp.person"", ""pk"": 2, ""fields"": {""name"": ""Johnny""}}, 
  {""model"": ""myapp.person"", ""pk"": 3, ""fields"": {""name"": ""Mom""}}, 
  {""model"": ""myapp.person"", ""pk"": 4, ""fields"": {""name"": ""Dad""}}, 
  {""model"": ""myapp.relation"", ""pk"": 1, ""fields"": {""parent"": 3, ""child"": 1}},
  {""model"": ""myapp.relation"", ""pk"": 2, ""fields"": {""parent"": 3, ""child"": 2}},
  {""model"": ""myapp.relation"", ""pk"": 3, ""fields"": {""parent"": 4, ""child"": 1}}, 
  {""model"": ""myapp.relation"", ""pk"": 4, ""fields"": {""parent"": 4, ""child"": 2}}
]
}}}
4. rename the `Person` model to e.g. `Foo` and update all references in code
5. run `makemigrations` and `migrate` again

== What happens

The `migrate` command fails with

{{{
django.db.utils.IntegrityError: The row in table 'myapp_relation' with primary key '1' has an invalid foreign key: myapp_relation.child_id contains a value '1' that does not have a corresponding value in myapp_person.id.
}}}

But a `Person` with `id=1` does exist in the database.

== What I would expect to happen

I would expect this to work without any problems.

== Notes

I also tried the same steps with an ''implicit'' `through` model , i.e. `children = models.ManyToManyField(to='self', blank=True)`.
This works without issue."	Bug	new	Uncategorized	4.2	Normal				Unreviewed	0	0	0	0	0	0